The subject invention pertains generally to metering active electrical energy by solid state electronic techniques and more particularly in one aspect relates to metering active electrical energy (for example, kWh) in three-wire, single phase electrical systems.
Electrical energy (kWh) has been and continues to be metered with the familiar rotating disk-type of meter. In addition, the instrumentation and metering arts include proposed systems having apparatus employing electronic and solid state devices for measuring power and energy. In such apparatus, electronic and solid state devices replace the conventional rotating disk.
Further, there is disclosed and claimed in applicant's copending applications, referred to above, apparatus and methods for metering electrical energy in an electrical system which involves producing analog signals from line currents and voltages. Pairs of analog signals representing current and voltage variables are processed in time divison multiplier networks which multiply the analog signals to produce a series of width and amplitude modulated pulse signals, each representing instantaneous partial power in a polyphase system and instantaneous total power in a single phase system. In the general case of a polyphase system, pulse signals from different multiplier networks are summed to provide another series of pulse signals each representing instantaneous total power. The series of pulse signals representing instantaneous total power are processed through a low pass filter to produce another signal representative of average total power in the system. Subsequently, the signal representing average total power is processed in an analog-to-pulse rate converter which produces a series of output pulse signals each representing a quantized amount of electrical energy. A stepping switch and register perform conventional accumulation, storage and display functions in response to the series of output pulse signals delivered thereto.
In the past, when more than one current variable was being detected, a corresponding number of multiplier networks has been required in order to provide an output signal which was directly proportional to the product of the sensed currents and the voltage variable. Because of the electronics utilized in the multiplier and because of space requirements, it has become desirable to provide an electrical metering system wherein more than two electrical current variables can be detected and multiplied by a single multiplier circuit to provide a composite signal representative of the power flowing in a single phase, multi-wire system.
It therefore is an object of the present invention to provide a method and apparatus for use in a solid state elecrical energy metering system for multiplying electrical analog signals representing voltage and at least two current variables in a power consuming system to produce a series of amplitude and pulse width modulated pulses.
It is another object of this invention to provide such a multiplier apparatus and method utilizing solid state circuitry which may be fabricated in the form of monolithic integrated structures.
It is yet another object of this invention to provide such a method and apparatus for use in a solid state electrical energy measuring system wherein either a feedback type or a direct type multiplier circuit can be utilized to generate a composite signal representing the power consumed in a single phase, multi-wire system.